Frontispiece: A Novel Cathode Material for Cathodic Dehalogenation of 1,1‐Dibromo Cyclopropane Derivatives

Development and Scale-Up of the Electrochemical Dehalogenation for the Synthesis of a Key Intermediate for NS5A Inhibitors

The electrochemical 2-fold dehalogenation of a spirocyclopropane-proline derivative at leaded bronze was scaled-up in a divided batch-type electrolysis cell in good yield and excellent selectivity. The upscaling via a flow electrolysis cell was also successful. Conditions were elaborated employing a single cell passage for complete conversion. The keys here are the direct cooling of the cathode and ensuring a good laminar flow.

A Novel Cathode Material for Cathodic Dehalogenation of 1,1-Dibromo Cyclopropane Derivatives.

Leaded bronze turned out to be an excellent cathode material for the dehalogenation reaction of cyclopropanes without affecting the strained molecular entity. With this particular alloy, beneficial properties of lead cathodes are conserved, whereas the corrosion of cathode is efficiently suppressed. The solvent in the electrolyte determines whether a complete debromination reaction is achieved or if the process can be selectively stopped at the monobromo cyclopropane intermediate. The electroorganic conversion tolerates a variety of functional groups and can be conducted at rather complex substrates like cyclosporine A. This approach allows the sustainable preparation of cyclopropane deriva…